Highly Linear Power Amplifiers (“HLPAs”) to achieve high spectral efficiency transmission systems are required in a number of contexts. For example, multimode, multicarrier wireless networks, including wideband existing and future cellular systems, including small cellular base stations and distributed antenna systems with reduced coverage areas and low transmit-power architectures all require HLPAs.
RF power amplifiers are typically non-linear. Methods to linearize the output are costly but necessary to achieve desired results. RF power amplifiers are typically operated a few dB backed off from maximum saturation power levels to maintain sufficient linearity. This back off, however, degrades the efficiency of the power amplifiers and exacerbates the thermal management of the power amplifier. These problems are not unique to RF power amplifiers. Indeed, all types of amplifiers demonstrate non-linear characteristics.
It is thus desired to minimize the amount of back-off necessary to maintain the highest efficiency and lowest power dissipation through the use of linearizers.